Find all School-related info fast with the new School-Specific MBA Forum

It is currently 29 May 2016, 03:30
GMAT Club Tests

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

the last digit of 3^3^3

  post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Manager
Manager
User avatar
Joined: 14 Aug 2009
Posts: 123
Followers: 2

Kudos [?]: 97 [0], given: 13

the last digit of 3^3^3 [#permalink]

Show Tags

New post 18 Aug 2009, 09:00
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 100% (00:25) wrong based on 1 sessions

HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

I took the free test of GMAT club. One of the questions is as below.

I choose that "the last digit is 3", but the answer key says "the last digit is 7". The answer key is incorrect, isn't it?
Attachments

2009-08-18_224452.png
2009-08-18_224452.png [ 2.65 KiB | Viewed 1246 times ]


_________________

Kudos me if my reply helps!

Current Student
User avatar
Status: What's your raashee?
Joined: 12 Jun 2009
Posts: 1847
Location: United States (NC)
Concentration: Strategy, Finance
Schools: UNC (Kenan-Flagler) - Class of 2013
GMAT 1: 720 Q49 V39
WE: Programming (Computer Software)
Followers: 22

Kudos [?]: 229 [0], given: 52

Reviews Badge
Re: the last digit of 3^3^3 [#permalink]

Show Tags

New post 18 Aug 2009, 10:26
flyingbunny wrote:
I took the free test of GMAT club. One of the questions is as below.

I choose that "the last digit is 3", but the answer key says "the last digit is 7". The answer key is incorrect, isn't it?


well that reduces into 3^27 right? now you should know the pattern of 3^p is:
1,3,9,7,1,3 etc. starting from p=0. so 28/4 7. So you get to 7. 28 is 27 (1-27) + 1(0th power). It is also simple to count if you really wanted.
Just to clarify - since the pattern for 3^p happens every 4 powers when you divide the power by 4 the remainder determines the position of the digit. In this example .25 = 1, .5=3,.75=9, 1 (or nor remainder) = 7.
_________________

If you like my answers please +1 kudos!


Last edited by shaselai on 18 Aug 2009, 10:30, edited 1 time in total.
SVP
SVP
User avatar
Joined: 29 Aug 2007
Posts: 2492
Followers: 65

Kudos [?]: 657 [0], given: 19

Re: the last digit of 3^3^3 [#permalink]

Show Tags

New post 18 Aug 2009, 10:29
flyingbunny wrote:
I took the free test of GMAT club. One of the questions is as below.

I choose that "the last digit is 3", but the answer key says "the last digit is 7". The answer key is incorrect, isn't it?



Follow here: last-digit-of-a-power-70624.html

You find some good discussions and concepts.
_________________

Verbal: new-to-the-verbal-forum-please-read-this-first-77546.html
Math: new-to-the-math-forum-please-read-this-first-77764.html
Gmat: everything-you-need-to-prepare-for-the-gmat-revised-77983.html


GT

Manager
Manager
User avatar
Joined: 14 Aug 2009
Posts: 123
Followers: 2

Kudos [?]: 97 [0], given: 13

Re: the last digit of 3^3^3 [#permalink]

Show Tags

New post 18 Aug 2009, 11:30
http://en.wikipedia.org/wiki/Exponentiation

according to this, the answer of "the last digit of 3^3^3" should be 7.

if you know the sequence of computing exponentiation, this question is a piece of cake, otherwise you would never get the answer right.
_________________

Kudos me if my reply helps!

Re: the last digit of 3^3^3   [#permalink] 18 Aug 2009, 11:30
Display posts from previous: Sort by

the last digit of 3^3^3

  post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.